1. Field of the Invention
The present invention relates to a fuel injection control device that adjusts a pumping quantity of a fuel supply pump with a metering valve and to a fuel injection system using the fuel injection control device, the fuel supply pump supplying fuel to an injector of an internal combustion engine.
2. Description of Related Art
There is conventionally known a technology of adjusting a pumping quantity of a fuel supply pump, which supplies fuel to an injector of an internal combustion engine, with a metering valve to control pressure of the fuel supplied to the injector. The metering valve is electromagnetically driven by current or the like to adjust the pumping quantity of the fuel supply pump. If a current value for driving the metering valve changes, the pumping quantity of the fuel supply pump changes.
The pumping quantity of the fuel supply pump varies due to an individual difference or aging of the fuel supply pump and the like. Therefore, it is preferable to calculate a learning value for controlling a drive amount of the metering valve based on a deviation between pressure of fuel supplied to the injector and target fuel pressure during one trip from an operation start to an operation end of the internal combustion engine and to control the drive amount with the learning value to approximate actual fuel pressure to the target fuel pressure (for example, as described in JP-A-2005-147005).
When the internal combustion engine is started in a next trip, the learning value learned in the present trip can be used as a start timing learning value for controlling the drive amount of the metering valve at a startup of the next trip.
In a case where an event that has caused the learning of the drive amount of the metering valve during the present trip is specific to the present trip, the event as the cause of the learning has been solved by the time of the engine startup of the next trip in some cases. For example, in some cases, a sliding failure of a sliding portion of the metering valve or deterioration of fuel properties during the present trip has been improved by the time of the engine startup of the next trip.
If the learning value of the present trip is used as the start timing learning value of the next trip in such the state, there is a possibility that when the drive amount of the metering valve is learned to excessively reduce the pumping quantity of the fuel supply pump in the present trip, the pumping quantity of the fuel supply pump is reduced at the startup of the next trip and eventually injection pressure of the injector falls excessively below the target injection pressure, causing an engine startup failure, for example.
If the drive amount of the metering valve is learned to excessively increase the pumping quantity of the fuel supply pump in the present trip, there is a possibility that the pumping quantity of the fuel supply pump at the startup of the next trip increases and eventually the injection pressure of the injector becomes excessively higher than the target injection pressure, causing a large combustion noise.